You are trying to decide which cell phone plan to purchase. plan a chargeres $40 for a new phone and $20 a month for usage. plan b provides the phone for free, but has a fee of $30 a month for usage.
use the substitution method to determine when the two plans will cost the same.

When george started his current job, his employer told him that at the end of the first year, he would receive two vacation days. after each year worked, his number of vacation days will double up to five work weeks (25days) of payed vacation. how many vacation days will he have in 4 years